This invention relates to a fuel cell cooling system using an antifreeze loop to supplement the cooling capacity of the liquid cooling loop.
Fuel cells are increasingly used for transportation applications. Fuel cells having proton exchange membranes (PEM) for these applications require large radiators to achieve a desired water balance within the fuel cell at high altitudes and/or high ambient temperatures. The fuel cell includes a stack having a cathode, anode and PEM electrolyte. The stack coolant inlet temperatures typically must be less than 60° C. to achieve the desired water balance. As a result, in one example, a radiator must be capable of rejecting between 70-80 kW of heat while providing a coolant return temperature to the fuel cell of less than 60° C.
The cell stack typically includes a liquid cooling loop, and an intermediate heat exchanger is used to separate the liquid coolant loop from an antifreeze that circulates through the radiator. The antifreeze is needed to prevent the radiator from freezing so that the fuel cell can operate in cold weather applications.
It is also desirable to operate the fuel cell near ambient pressure. Therefore, what is needed is a cooling system operating at near ambient pressure and at a temperature of 60° C. or lower in the fuel cell while rejecting heat from the antifreeze/water loop at higher temperatures to minimize radiator size.